Jonathan Safran Foer's Everything Is Illuminated is divided between two voices. One belongs to a would-be novelist called Jonathan Safran Foer, who is on a pilgrimage to the Ukrainian village where his grandfather somehow survived the annihilation of its Jews by the invading Germans. The other belongs to his translator, Alex, who relies on a thesaurus for much of his English vocabulary. A thesaurus, of course, leads the user to associated rather than exactly synonymous words. So while Alex's syntax is fairly accurate, his vocabulary is dependably wrong. "I dig to disseminate very much currency at famous nightclubs in Odessa." "You were perhaps accounting upon a translator with more faculties," he concedes to Jonathan, before proudly adding, "but I am certain that I did a mediocre job."

Alex presumes that the longer or more Latinate word is the better one, like many word-blunderers before him. He has "a miniature brother" who is "always promenading into things". He is "unequivocally tall". Yet this also leads him to words that get neglected in colloquial usage. His father makes him feel "wrathful"; his grandfather "conceals his melancholy with mastery"; they and he are "the primogenitory children in our families". Wouldn't it be good if these words did get their opportunities in everyday speech?

Alex's trait is a special kind of malapropism, a linguistic habit named after a literary character, Mrs Malaprop in Sheridan's comedy The Rivals (1775). She gets her name from the French phrase mal-à-propos (inappropriate, inopportune) and is decisive in her use of the wrong word. "He is as headstrong as an allegory on the banks of the Nile!" Though she gave the error its name, there were characters before her who did the same thing. In drama, you can go back to Dogberry in Shakespeare's Much Ado About Nothing. "Comparisons are odorous." Novels, with their attention to the revealing of character by speech, have often featured malapropism lovers. One of the earliest English novels, Fielding's Joseph Andrews, features an amorous housekeeper with ideas above her intellect, who regularly baffles the hero with her pronouncements. "Barbarous Monster! How have I deserved that my Passion should be resulted and treated with Ironing?" Unsurprisingly, given his interest in colloquial expressiveness, Dickens gave some of his characters fitting malapropisms. Think of Mr Bumble, the appalling and absurd beadle in Oliver Twist, with his "We name our fondlings in alphabetical order" (when fondness really doesn't come into it).

More recently, Barbara Kingsolver's The Poisonwood Bible has, as one of its narrators, Rachel Price, a teenager wedded to the wrong words. Arriving in the Congo, her squeamishness is aptly caught by her absurd diction. "We got fumigated with the odor of perspirating bodies ... We just got shoved straight into the heathen pandemony." No wonder she declares herself "in the sloop of despond." This creatively mangled idiom might equally have been used by another modern Malaprop, Drenka, the protagonist's implausibly lustful Croatian mistress in Philip Roth's Sabbath's Theatre. When she is dead, Mickey Sabbath grievingly recalls "as many as he could of Drenka's malapropisms": "bear and grin it", "his bark is worse than your cry", "his days are counted", "the boy who cried 'Woof!'" The comedy is partly in the inadvertent wit.

Most of Mrs Malaprop's kin use the wrong polysyllabic words, making mistakes because they strain to impress. Alex uses words that are only just out - one step away from what would have been idiomatically correct. Often they are inappropriate synonyms - he signs his letters not "sincerely" but "guilelessly". His errors are often curiously expressive. "I luxuriated the receipt of your letter," he writes to Foer's alter ego. What indeed could be a more appreciative response? "I hanker for this letter to be good ... In Russian my ideas are asserted abnormally well, but my second tongue is not so premium." But then Safran Foer has coined an idiolect - a distinctive use and misuse of English - for this narrator in order to approach his grave subject indirectly. It is Alex the incompetent translator on whom we come to rely as the novel unearths the story of a massacre and of one man's betrayal of his Jewish friend. In the end, fumbling to imagine such things, his company is not a bad guide.

• John Mullan is senior lecturer in English at University College London